The invention is especially applicable to driven bogies which comprise a bogie frame, typically comprising longitudinal and lateral beams; two or more wheelset units, which may include a drive unit and/or brake unit, connected with the bogie frame via a primary suspension, or a linkage and a primary suspension; and a secondary suspension, or a center pin or similar device and a secondary suspension, for connecting the bogie frame to a car body.
For such bogies, it is desirable that the wheelsets, depending on the longitudinal stiffness of the primary wheelset linkage or suspension, can adjust themselves in a curved track. A large number of such bogies with radially adjustable wheelsets have been disclosed. With the majority of these bogies, as disclosed, for example, in German patent specifications DE 31 19 164 C2 and DE 32 32 289 A1 and WIPO patent specification WO 90/02068 which are incorporated herein by reference, more or less rigidly linked coupling mechanisms are used, arranged between the wheelsets, or between the wheelsets and the car body. Also known is the mechanical coupling of a wheelset with a drive unit, which--by the arrangement of the coupling elements--allows the wheelset to swivel about an ideal or real pivoting point situated before or behind the wheelset in the direction of travel. Also, indirect mutual support of axle drives in conjunction with wheelset coupling elements is disclosed in European patent application 0 072 535 A1, incorporated herein by reference.
Because they involve many components, these known bogies are costly to assemble and to maintain, and they involve close tolerances.
Some bogies allow more or less free adjustment of the wheelsets due to very low rates of longitudinal stiffness in their primary linkage. However, since the primary linkage must also transfer the tractional forces during starting and braking, the forces adjusting the wheelset are interfered with or compensated for. The resulting parallel displacement of the wheelset must be limited because of the inherent geometry of the drive and the brake. This also results in limiting of the mutually opposite longitudinal travels of the primary linkage required for wheelset adjustment.
When wheelsets are driven by drive motors or power takeoffs suspended from the car body, via a drive shaft and axle drive, a turn-out movement of the bogie requires the drive shaft, which is arranged between the vehicle body and the bogie, to change its length (EP 0 072 535).
When drive momentum is transferred during passage over an inward or outward curve, a change in length requires extension forces, which can increase the turn-out resistance of the bogie several fold, and which--especially at high rates of drive performance--hamper or make impossible the free adjustment of the bogie to the curve.
It is therefore an object of the present invention to eliminate or at least mitigate the foregoing deficiencies and create an improved bogie, and in particular a traction bogie.
According to the present invention there is provided a bogie, for rail vehicles, comprising a bogie frame, two or more wheelset units, at least one of the wheel set units comprising least one of a drive unit, brake unit and wheelset coupling frame connected thereto, a primary suspension connecting the wheelset units to the bogie frame, a secondary suspension for connecting a vehicle body to the bogie frame, and a rigid guide rod for coupling between the bogie and a vehicle body, the guide rod being coupled at its one end to said one of said wheelset units at or as close as possible to an inertial pole thereof.
Such coupling at, or as close as possible to the inertial pole of the wheelset or drive unit, or at the vertical axis of the mass moment of inertia, tends to, avoid the occurrence of parasitic moments when traction forces are applied in curves, which would lead to a maladjustment of the wheelset. If the guide rod acts at a point located outwardly thereof, a parasitic moment develops when the bogie turns outward and at the same time traction forces occur, and this leads to maladjustment of the wheelset in the track.
Advantageously, in embodiments of the invention, the transmission of the traction forces is such that the wheelsets are allowed only a certain adjustment behavior determined by the forces of the wheel/track geometry, and the bogie frame is left to perform only "carrying" and "guiding" functions. An advantage of bogies embodying the invention is that they are easy to assemble and service, and do not require the highest of tolerances.
It is advantageous to have the guide rod flexibly mounted in non-wearing elastomeric elements capable of withstanding cardanic stress i.e., stress from any direction so that the longitudinal forces can be transferred without being controlled.
In the case of non-driven wheelsets, coupling can be established via a centrally arranged bearing or via a bifurcated shaft coupled to the wheelset bearings. In the case of driven wheelsets, the guide rod can be coupled close to the center of gravity of a drive unit elastically or rigidly connected with the wheelset.
Coupling of the wheelsets can be established individually or in such a way that both wheelsets are coupled with each other inside the bogie, and a common coupling is made via the guide rod to the vehicle body. In this case, two wheelsets, for example, can be coupled in such a way that the adjustment behaviour of the individual wheelsets is not affected, or a specific radial adjustment of both wheelsets, e.g., via a common central linkage point, can be achieved.
Embodiments of the invention make it possible to neutralize the traction moments that occur during starting or braking, especially when axle suspension motors or drives elastically supported on both sides of the wheel or on the wheelset shaft are used. To ensure that the turning movements of the wheelsets are not interfered with by the rigidly or transversely elastically mounted drive or brake units, the latter are advantageously suspended from the main cross beam of the bogie via pendulums.
A sufficiently soft design of the lateral characteristic of the common coupling and of the primary wheelset linkage allows the wheelsets to evade lateral disturbances individually, without transferring these to a considerable degree between both wheelsets.
If the arrangement of a single central coupling point in conjunction with the longitudinal stiffness of the linkage at the wheelset bearing is not enough to achieve a higher speed through stable travel, it can be replaced by paired coupling points or elements that can slide outwardly at random. The maximum speed can be further increased according to the invention by combining a coupling frame which connects all wheelset bearings at defined rates of elasticity, and which facilitates the use of fully elastic quill drives.
In the case of vehicles driven by a drive shaft and an axle drive, the coupling is arranged parallel to the drive shaft, with the guide rod having the same length as the drive shaft between the universal joint centers. This eliminates any change in length during outward-turning of the bogie. It is practical to integrate the momental support required at the axle drive into a bifurcated guide rod; the guide rod connecting two adjacent axle drives may be designed in a similar fashion.